Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 57)

AP200 CO
2
/H
2
O Atmospheric Profile System
If seq_ACTIVE is True, then set STOPsequence = True to stop the
sequence, and then verify seq_ACTIVE changes to False.
Variable cell_press is the pressure in the IRGA sample cell. Set pump_ON =
False to turn the pump off and it should be possible to hear the pump stop.
Wait for the value of cell_press to rise and stabilize to ambient pressure. This
may take several minutes as the intake tubes and mixing volumes fill with air.
Make sure the dewpoint generator is connected to the H
2
O Span inlet as shown
in Section 5.2.3, H
2
O Span. Consult the dewpoint generator’s user manual for
proper operation of the dewpoint generator.
Enter the dewpoint generator’s temperature setpoint (in °C) for
H2OSpanDewPt.
While the pump is off and the IRGA sample cell is still at ambient pressure, set
SETpressAmbient = True. The AP200 will store the value of cell_press in
PRESS_AMBIENT. Verify that the value in PRESS_AMBIENT now
matches cell_press.
The next two variables are Td_cell and Td_ambient. Td_cell is the dewpoint
temperature measured by the IRGA. Td_ambient is corrected for the
difference in pressure between the sample cell and ambient (see Appendix I,
Useful Equations). With the pump off, these two dewpoint temperatures
should match.
Step down to pump_ON and set it to True to turn the pump on. It should be
possible to hear the pump start to run at full speed and then slow down to
stabilize the pump pressure to its setpoint.
While the pump is on and the IRGA sample cell is stable at its normal
operating pressure, set SETspanCellP = True. The AP200 will store the value
of cell_press in SpanCellP. Verify that the value in SpanCellP now matches
that of cell_press.
Set valve_number to H2Ospan (11). Look at the LEDs on the valve module
to confirm the H
2
O span valve is now active.
Check the value of diag_AP200. If it is not zero, a problem in the AP200
system should be resolved before continuing (see Appendix B, AP200
Diagnostics).
Wait for the value of Td_ambient to stabilize. This normally takes one to two
minutes.
Set DO_H2O_span to True. The AP200 will send the command to the IRGA
to do an H
2
O span. While the IRGA is setting the span, the value for
Td_ambient will not be available and NAN will be displayed. This will take
approximately 10 s. When the process is complete, Td_ambient will again be
displayed. Verify that the value is close to the value of H2OSpanDewPt.
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